1. Field of the Invention
This invention relates to a dry cleaning method and a dry cleaning apparatus for the method using an organic solvent, such as tetrachloroethylene, for a cleaning fluid.
2. Description of the Related Art
In a general dry cleaning using an organic solvent, such as tetrachloroethylene, for a cleaning fluid, pre-cleaning and main cleaning are acted in each predetermined time by using a solvent mixed with a cleaning agent including an oil-soluble surface-active agent in batch process or to be circulated through a filter.
The solvent used in the pre-cleaning or the main cleaning is recycled by purification through distillation and condensation processes because it is not allowed to dispose the solvent to sewerage and price of the solvent is high.
If the solvent is not distilled completely, remained dirt in the solvent not removed by distillation may stick again to cleaning objects as reverse contamination when the solvent is reused. For preventing the reverse contamination, it is already proposed to control volume of distillation correspondingly to absolute contamination level of the used solvent detected by a sensor. It is shown in Japan Utility Model Application Laid-open S57-160651.
Objects to be Solved
The oil-soluble surface-active agent used together with the solvent for pre-cleaning and main cleaning has lipophilic group and hydrophilic group. The surface-active agent adheres to aqueous dirt on the cleaning objects and penetrates into the cleaning objects so as to generate reversed micellar disposing lipophilic group outwardly by enclosing the dirt. Thereby, the aqueous dirt is removed from the cleaning objects, so that the reversed micellar exists as dirt component in the used solvent.
When the used solvent is distilled, solvent having low boiling point is vaporized and the reversed micellar having high boiling point stays as residue. The residue may be finally disposed of as industrial waste.
It shall be avoided for protecting environment to generate the industrial waste in process of distilling the used solvent. Additionally, it is confirmed by the applicant that aqueous dirt of the cleaning objects can be washed off by using moisture in the air. Dry cleaning without surface-active agent becomes to be realized.
In the general dry cleaning, pre-cleaning and main cleaning are acted by using the used solvent mixed with the cleaning agent in batch process or to be circulated through a filter. In the dry cleaning without surface-active agent, the used solvent without cleaning agent is collected continuously from the process tank, and whole volume of the solvent is flown back to a base tank by purification through distillation and condensation processes. On the other hand, The pure solvent is supplied continuously from the base tank to the process tank for replenishment. Thus, cleaning and rinsing can be acted continuously without a filter.
According to the dry cleaning without surface-active agent, generating industrial waste by the residue of the reversed micellar can be eliminated. The purified solvent is replenished continuously to the process tank, so that the required net volume of the solvent for total can be reduced in comparison with usual dry cleaning which washes the cleaning objects without intermediate replenishment of the solvent by supplying previously larger volume of the pure solvent. Therefore, the dry cleaning according to this invention has a big advantage for environmental issue.
According to the dry cleaning without surface-active agent, it is no chance that the same solvent in the process tank is used continuously for long time. Thereby, monitoring absolute contamination level of the used solvent for adjusting vaporized volume of the used solvent is not required.
According to the usual dry cleaning, the whole solvent used for cleaning is replaced periodically. In the dry cleaning without surface-active agent according to this invention, pre-cleaning and main cleaning are acted continuously by circulating the same solvent which is purified through distillation and condensation processes. Therefore, time for pre-cleaning or main cleaning determined for the usual dry cleaning cannot be applied for the dry cleaning according to this invention. In this dry cleaning, it is very important how suitable stop timing of the dry cleaning process is determined.
To have solutions for above issues, one object of this invention is to provide a dry cleaning method for dry cleaning without surface-active agent by acting simultaneously cleaning and purification of the solvent by distillation, in which a suitable stop timing of the dry cleaning process can be known easily and a dry cleaning apparatus suitable to be used for performing the dry cleaning method.